1. Field of the Invention
The present invention relates to a bicycle derailleur, and more particularly, to a derailleur for a chain bicycle to permit forward motion of the bicycle by either forward or reverse rotation of the bicycle's pedals.
2. Description of the Related Art
Bicycle riding is excellent exercise. Vigorous biking is wonderful for general body health in that it produces increased heart rate to supply increased blood to the large leg muscles. Further, the constant leg impact associated with jogging is not present.
In the basic bicycle design, a rear wheel of the bicycle is driven by a bicycle chain through a chain sprocket powered by a pedal shaft driven by the legs and feet of the bicyclist operating on a pair of bicycle pedals attached to the pedal shaft.
For the typical bicycle to move in a forward direction, the bicyclist applies force to the pedals causing them to rotate in the same rotational direction as a front wheel of the bicycle for forward motion. This rotational direction is hereinafter referred to as the “forward direction”, and an opposite rotational direction is hereinafter referred to as the “reverse direction”. Accordingly, the rotational direction of all components of the bicycle will be explained as the forward or reverse direction.
As one kind of currently used typical bicycles, a bicycle which permits a forward force to be applied to a bicycle's drive wheel by either forward or reverse rotation of the bicycle's pedals is known.
An example of the bicycle to permit forward motion of the bicycle with either forward or reverse rotation of the bicycle's pedals is disclosed in UK Patent Laid-open Publication No. 2143599. The disclosed bicycle comprises: two rear wheel sprockets rotatably mounted on a rear wheel shaft via respective one-way clutches along with a rear wheel hub, the clutches being adapted to transmit power in only a forward direction of the bicycle's rear/drive wheel; and an idler sprocket rotatably mounted to a bicycle frame. The bicycle further comprises an endless chain looped around a pedal sprocket as well as both the rear wheel sprockets and the idler sprocket.
In the prior art bicycle configured as stated above, the two rear wheel sprockets drive a rear wheel hub only when they rotate in a forward direction, and rotate separately from the rear wheel hub when they rotate in a reverse direction. Such an arrangement of the two rear wheel sprockets on the rear wheel shaft causes the two rear wheel sprockets to rotate in opposite directions. That is, when one of the rear wheel sprockets rotates in the forward direction, the other sprocket must rotate in the reverse direction.
In addition to permit forward motion of the bicycle by either forward or reverse rotation of the bicycle's pedals, such a configuration as described above permits the bicycle to move forward with a high transmission gear ratio upon forward pedaling and with a low transmission gear ratio upon reverse pedaling.
However, the prior art bicycle, which moves forward by either forward or reverse pedaling, cannot perform transmission with a conventional gear-change means having a known pantograph linkage because the single endless chain surrounds the two rear wheel sprockets. This makes it impossible for the bicyclist to perform transmission upon forward pedaling.